Method of reducing the octane requirement of an engine



United States Patent Ciiice 2,725,856 Patented Dec. 6, 1955 METHOD OFREDUCING THE OCTANE REQUIREMENT OF AN ENGINE John D. Bartleson,Franklin, Mich., assignor to The saongard Oil Company, Cleveland, Ohio,a corporation to No Drawing. Application January 11, 1954, Serial No.403,436

5 Claims. (Cl. 123-1) The present invention relates to a method of andcomposition for reducing the tendency of an internal combustion engineto knock.

It is well known that deposits quickly accumulate in the combustionchambers of internal combustion engines such as those used inautomobiles. An engine containing deposits is said to have a higheroctane requirement than a clean engine because it requires a gasolinewith a higher octane rating if the engine is not to knock. This becomesapparent to the driver of an automobile having a dirty engine by thetendency of the engine to knock while accelerating, climbing a hill orotherwise operating the engine under greater than normal load. Thedeleterious effects of such accumulations of deposits are particularlynoticeable in engines having a high compression ratio because the marginbetween the octane numbers of gasolines on the market and the octanerequirement of the engine when clean is narrower than for engines havinglower compression ratios. When such an engine becomes dirty the octanenumber of the gasoline required by the engine in order not to knock isincreased and often reaches a value higher than the octane rating ofgasolines generally available.

When the fuel used in an internal combustion engine contains tetraethyllead, an agent which in effect raises the octane rating of the fuel, theincrease in octane re- 4? quirement of the engine with continued usebecomes greater than when non-leaded fuels are used, especially undermild conditions simulating ordinary driving. Thus, whereas the octanerequirement of an internal combustion engine operating on non-leadedfuel under the conditions of a standard engine test describedhereinafter may increase from say 70 for a clean engine to 78 for adirty engine and then level olf at that figure, the octane requirementin the same engine, if run on leaded fuel, will increase to 82 or morefor a dirty engine before levelling off.

It has been found that the deposits in the combustion chambers ininternal combustion engines run on leaded fuel are different ondifferent surfaces, apparently because of their different averagetemperatures. In an aviation engine, for example, the metal temperaturesof the piston, cylinder intake valve and exhaust valve are 300 to 500,400 to 600, 600 to 800 and 1000 to 1200 F., respectively. Thecomposition of the deposits appears to depend on the metal temperatureof the particular surface. Where the metal temperature is of the orderof about 400 F. the deposits analyze about 5060% lead and consist offrom about to lead sulfite and lead sulfate, 20% lead monoxide, to leadbromide and about 15% carbon. Where the metal temperature isconsiderably higher, i. e., of the order of 1000 to 1200 F., the leadcontent is about 70% and the deposits are composed almost entirely oflead sulfate, lead sulfite and lead monoxide, the concentration of leadbromide being extremely small and the amount of carbon being practicallyzero. These observations are recorded in ASTM Bulletin, No. 154, October1948, page 53, Better Lead 2 Scavenging Needed for AviationDroegemueller.

It is well known, of course, that ordinarily the octane requirement ofan engine, whether it be an automobile, marine or airplane engine, isreduced in order to restore or at least to approach its originalefiiciency by the process of removing a cylinder head and grinding orabrading off the deposits found on the various surfaces of thecombustion chamber, such as the piston top, the cylinder wall, cylinderhead and the intake and exhaust valves. This method, while quiteeffective, has the disadvantage of requiring skilled labor and aconsiderable amount of time to dismantle, clean and reassemble theengine. It is therefore responsible, when carried out on engines ofcommercial vehicles, for making it necessary to withdraw the vehiclecompletely from service while the engine is being overhauled.

A great number of other methods have been proposed heretofore forcleaning the combustion chambers of an engine without removing thecylinder head. One of these methods is that of introducing a liquidsolvent into the carburetor while the engine is running. Although thismethod produces great billows of smoke at the exhaust, it has beenfound, upon taking apart an engine so treated, that little of thedeposits are actually removed.

In accordance with this invention the octane requirement of a dirtyinternal combustion engine, which term is intended to include sparkignition and fuel injection type engines, is reduced by coating thedeposit-bearing surfaces of the combustion chambers of a dirty enginewith a composition containing an inorganic boron compound selected fromthe group consisting of borates, boridcs and boranes of the alkali andalkaline earth metals. The coating of the combustion chamber wallsurfaces may be accomplished in any desirable manner, such as byspraying or squirting the composition into the combustion chamberthrough an opening such as that provided by removal of the spark plug orinjection nozzle. The composition to be applied to the dirty combustionchamber walls essentially comprises two components. One component ischemically reactive with lead or its compounds under the conditionswithin the combustion chambers of a running internal combustionengine'and comprises one or more borates, boridcs or boranes of alkalior alkaline earth metals. The other essentialcomponent performs thepurely physical function of adhering the reactive component to thecombustion chamber walls and is a thick, tacky, metal-adhering materialor mixture of materials that is fairly viscous or non-flowable atambient temperatures, non-corrosive to the engine parts, and preferablyvreadily removable from the combustion chamber by eventualvolatilization and/or combustion under the conditions in the-combustionchamber.

While it is to be understood that the scope of the invention is not tobe limited by any theory advanced herein, it is believed that the leadin the lead sulfate, lead sulfite and lead oxides forming the combustionchamber deposits is, by reason of its variable valence, in an activestate and probably exerts an unfavorable catalytic effect on thecombustion of the fuel in the engine. It is believed that by treatingthese lead salts with an inorganic boron compound, a binary compound isformed in the deposits in which the lead is comparatively inactive,since it can no longer move freely from, one valence state to another,and its catalytic action is thereby inhibited.

Gasoline, by E. A.

viscous and capable of adhering-to the combustion chamber walls andparticularly to the deposits on the walls.

Generally, the composition should contain at least 3 about 10% by weightboron compound to be effective and up to about 90% by weight to retainviscosity, stability and adhering power.

Borax is preferred as the boron-containing inorganic compound for thepurposes of this invention, chiefly be.- cause of its high boron contentand its availability .and low cost. It is to be understood, however,that other compounds of boron with alkali and alkaline earth metals,whileperhaps not as readily available or as inexpensive, may likewise beused in the method of this invention. Such other boron compoundsinclude:

Sodium metaborate NaBOz Sodium perborate NaBOa Sodium tetraboranideNazBiHio Potassium metaborate KBOz Potassium tetraborate K2340":Potassium pentaborate KBsOs Potassium perborate KBOa Potassium diboraneKzBaHs Potassium dihydroXy-diborane KzBzHsOz Potassium pentaboraneK2B5H9 Lithium metaborate LiBOz Lithium tetraborate LizBtOr Calciummetaborate Ca(BOz)z Calcium tetraborate CaBrOv Calcium boride CaBcBarium boride BaBs Strontium tetraborate SrBtOw Strontium boride SrBeBecause of the purely physical function of the vehicle or carriercomponent, its chemical composition and structure are not particularlycritical so long as it is capable of carrying the boron compound,adhering to metal and combustion chamber deposits, and does not damagethe engine. Generally, viscous and tacky hydrocarbons that are capableof being volatilized or consumed under the conditions of combustion inthe combustion chamber of a running engine and thereby removed, arepreferred as vehicles in the composition. Such vehicles or carriersinclude petroleum bright stocks, polybutenes, petrolatums, hydrocarbonoils thickened, if desired, to gel form with suitable thickening agentssuch as hydrogenated castor oil, and greases, particularly the softergreases. One type of vehicle that has been found particularly useful isa 50-50 mixture of a petroleum bright stock having a viscosity of about700-2300 SSU at 100 F. and a viscous synthetic polybutene having amolecular weight of about 1185.

The advantages and utility of the invention will become more apparentfrom the examples included herein for illustrative purposes only.

The following compositions, in which the proportions are by weight, arespread on piston tops having appreciable amounts of deposits coveringthe surface:

Vehicle Composition N Boratc sodium perborate 90% White Petrolatum.

2.. 00% sodium perboratc 10% White Petrolatum. 3 10% sodiuminetaborate... 90% White Petrolatum. 4,- 90% sodium metaborate... 10%White Petrolatum. 5.. ..do 10% Penn. Bright Stock. 6 50% sodiumtetraborate... 50% Equal parts of Penn.

Bright Stock and Polybutene.

Satisfactory adherence deposits is demonstrated approximate ordinarydriving conditions and dirty the engine. This procedure involves runningthe engine for five minutes at 2000 R. P. M., corresponding to a roadspeed of M. P. H. with-standard spark advance, an oil temperature of 190F., and a water temperature at the jacket outlet of 160 F., and thenrunning the engine for one minute at 500 R. P. M. under idlingconditions. This six minute cycle was repeated until the octanerequirement of the engine had arrived at an equilibrium value. Inmeasuring the octane requirement at intervals of about eight hours, theengine was operated under the following conditions:

Speed, R. P. M 1000 Load throttle full Jacket outlet 160 Oil temperature190 Spark advance l1 BTDC Air fuel ratio 13.5

After the octane requirement had risen from an initial of 70 to anequilibrium value of 79, Composition No. 6 listed above, consisting of amixture of 25% petroleum bright stock having a viscosity of 1550 SSU at100 F., 25% of a viscous synthetic polybutene (available commercially asoronite polybutene No. 32) having a molecular weight of about 1185, andboraX was coated on the combustion chamber walls of the dirty engine toa thickness of about A".

The engine testing procedure previously described was then resumed andthe octane requirement of the engine was measured after 1, 30 and 5 8hours of operation alternately at 2000 and 500 R. P. M. It was foundthat the octane requirement of the engine was 81 after the first hour,after 30 hours, and 74 after 58 hours.

These tests show that the borax effected a significant reduction inoctane requirements, thus indicating effectiveness in inhibitingundesirable catalytic action on the part of the engine deposits. It alsodemonstrates the prolonged elfects of the treatment in that even after58 hours of engine operation, which is equivalent to 2320 miles, theoctane requirement had risen only four octane units. It was observedthat the decrease in octane requirement was accompanied by improvedcompression and a 10% increase in engine power output.

It is to be expected that variations and modifications of this inventionwill readily occur to those skilled in the art upon reading the presentdescription. All such modifications are intended to be included withinthe scope of the invention as defined in the accompanying claims.

I claim:

1. A method of reducing the octane requirement of a dirty internalcombustion engine having lead-containing deposits on the surfacesforming the combustion chambers which comprises coating thedeposit-bearing combustion chamber surfaces with a compositionessentially comprising from about 10 to by weight of a viscous,metal-adhering vehicle that is non-corrosive to the engine parts andcontains from about 90 to 10% of an inorganic boron compound selectedfrom the group consisting of borates, borides and boranes of the alkaliand alkaline earth metals, and then running the engine.

2. The method defined in claim 1 in which the composition is sprayedinto the combustion chambers of the engine through the spark plugopenings thereof and the vehicle component of the composition is ahydrocarbon.

3. The method defined in claim 1 in which the composition is sprayedinto the combustion chambers of the engine through the spark plugopenings thereof and wherein the vehicle component of the composition isa mixture of equal parts by weight of a bright stock having a viscosityof about 700-2300 SSU at F. and a viscous synthetic polybutene having amolecular weight of about 1185.

4. The method defined in claim 1 in which the composition is sprayedinto the combustion chambers of the engine through the spark plugopenings thereof and in which the inorganic boron compound is borax.

5. A method of reducing the octane requirement of a dirty internalcombustion engine having lead-containing deposits on the surfacesforming the combustion chambers which comprises coating thedeposit-bearing combustion chamber surfaces with a compositionessentially comprising from about 10 to 90% by weight borax and fromabout 90 to 10% by weight of a mixture of equal parts by weight ofbr'ght stock having a viscosity of about 700-2300 SSU at 100 F. and apolybutene having a molecular weight about 1185, and then running theengine.

References Cited in the file of this patent UNITED STATES PATENTS154,130

6 1,749,312 Blair Mar. 4, 1930 2,089,580 Schulze Aug. 10, 1937 2,460,700Lyons Feb. 1, 1949 2,578,585 Orozco Dec. 11, 1951 5 2,614,985 Cook Oct.21, 1952 OTHER REFERENCES Pharmaceutical Formulas, vol. I, 12th Ed.,1953. Pub. by The Chemist and Druggist, London, pages 839 10 and 848pertinent.

Eggleston Aug. 18, 1874

1. A METHOD OF REDUCING THE OCTANE REQUIREMENT OF A DIRTY INTERNALCOMBUSTION ENGINE HAVING LEAD-CONTAINING DEPOSITS ON THE SURFACESFORMING THE COMBUSTION CHAMBES WHICH COMPRISES COATING THEDEPOSIT-BEARING COMBUSTION CHAMBER SURFACES WITH A COMOSITIONESSENTIALLY COMPRISING FROM ABOUT 10 TO 90% BY WEIGHT OF A VISCOUS,METAL-ADHERING VEHICLE THAT IS NON-CORROSIVE TO THE ENGINE PARTS ANDCONTAINS FROM ABOUT 60 TO 10% OF AN INORGANIC BORON COMPOUND SELECTEDFROM THE GROUP CONSISTING OF BORATES, BORIDES AND BORANES OF THE ALKALIAND ALKALINE EARTH METALS, AND THEN RUNNING THE ENGINE.